A great way (the only right way) to check for previous instances

				
Before I always used this code to check if a 
previous instance was already running, but it I wasn't happy with it as my 
floppy always started rumbling and it took some time to do the check. It even 
failed a few times.

bool AlreadyRunning = 
(Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName).Length > 
1);
 
This example is much faster and much more 
reliable:

C# 
code:

//Put the next line of code at the very 
top
using System.Runtime.InteropServices;

public const int ERROR_ALREADY_EXISTS = 
183;

[DllImport("Kernel32.dll", SetLastError = 
true)]
public static extern int CreateMutexA(int lpSecurityAttributes, bool bInitialOwner, string lpName);

[DllImport("Kernel32.dll", SetLastError = true)]
public static extern int GetLastError();

public bool 
IsProcessAlreadyRunning()
{
    //Attempt to create defualt mutex owned by process, MyApp can e.g. be the 
name of the executable
    CreateMutexA(0, 
true, 
"Automove");
    return (GetLastError() == 
ERROR_ALREADY_EXISTS);
}


VB.NET Code:

'Put the next line of 
code at the very top
Imports System.Runtime.InteropServices

Public Const 
ERROR_ALREADY_EXISTS As 
Integer = 
183

Public 
Declare Function CreateMutexA Lib "Kernel32.dll" (ByVal lpSecurityAttributes As Integer, ByVal bInitialOwner As Boolean, ByVal lpName As String) As Integer

Public Declare 
Function GetLastError 
Lib "Kernel32.dll" () 
As Integer

Public Function IsProcessAlreadyRunning() As Boolean
    'Attempt 
to create defualt mutex owned by process, MyApp can e.g. be the name of the 
executable
    CreateMutexA(0, 
True, 
"MyApp")
    
Return (GetLastError() = 
ERROR_ALREADY_EXISTS)
End Function
Hope this is of some 
help.